Experimental studies in the lens shock tunnel and expansion tunnel to examine real-gas effects in hypervelocity flows

Measurements and analyses are presented from a combined experimental and numerical program to examine the separate and combined effects of viscous/inviscid interaction and real gas chemistry on ground test facility performance and the aerothermal characteristics of vehicles in hypervelocity flows. The results of earlier studies to examine real gas effects are reviewed. The major features of the LENS reflected shock tunnels and the LENS X expansion tunnel are presented together with measurements and numerical simulations to calibrate and validate their performance for velocities up to 15 kft/s. The results of the most recent experimental studies conducted in the LENS I and 48-inch shock tunnel together with "state-of-the-art" Navier-Stokes and DSMC predictions are presented demonstrating that, in the absence of real gas effects, complex regions of laminar shock wave/boundary layer interaction in hypervelocity flow can be accurately described by experienced computationalists. Surface and flowfield measurements on the double cone configuration in studies in LENS I and LENS X with nitrogen and air at velocities of 14kft/sec indicate that real gas effects can significantly decrease the separation length and the heating in the reattachtment/shock/shock interaction regions. Comparisons with Navier-Stokes predictions suggest that the current models for air chemistry used in these codes are not sufficiently accurate to allow good predictions of the size and properties of the interaction region for airflow velocities of 14 kft/s.